This invention relates to suppression of undesirable electrification tending to occur at an outer surface of a display front of a cathode-ray tube which can be used as, for example, a picture tube of a television receiver, a display unit in a terminal equipment of a computer or a display unit of an oscilloscope.
In a cathode-ray tube in which a phosphor screen (a metal back film) formed on an inner surface of a glass bulb is scanned by an electron beam, the phosphor screen is maintained at a potential of an anode supplied with a high voltage. Consequently, an outer surface of a panel portion of the glass bulb tends to be electrified and will have a high potential which will provide various adverse effects such as impartation of electric shocks to a user or viewer and generation of electric discharge causing mal-operation of electronic equipments located in the neighborhood of the cathode-ray tube.
Various proposals were made in the past so as to deal with such problems. For example, JP-U-62-131356 (laid open on Aug. 19, 1987) and JP-U-63-19755 (laid open on Feb. 9, 1988) disclose a cathode-ray tube of a type having a front glass layer provided on an outer surface of a panel portion of the tube. In the disclosed cathode-ray tube, a transparent, electrical conductive film is formed on a surface of the front glass layer opposite to the panel portion or on the outer surface of the panel portion, and this electrical conductive film is grounded so as to prevent appearance of a high potential at the outer surface of the display front of the cathode-ray tube.